Journal of Natural Disaster Science

AN EVALUATION OF REGIONAL SEISMIC RISK POTENTIAL IN JAPAN AS EMPHASIZED ON DISASTER SEQUENCES

Yutaka OHTA
Professor, Faculty of Engineering, Hokkaido University

(Received Oct. 22, 1985 and in revised form Dec. 23, 1985)

Abstract

A study of regional seismic risk evaluation with particular emphasis on disaster sequences was made based on the hypothesis that disasters caused by a certain seismic input are determined uniquely as the outputs of a receptor system of a region of which characteristics are described by a combination of environmental indicators.

A general set of disaster-governing equations was first constructed and then reduced to simple equations with which we could simulate the major part of causal and sequential character of the aspects of disasters inherent in an earthquake. After verification with reference to past earthquake disaster data, a comparative evaluation of the seismic risk potential in each of the 47 prefectures of Japan was made to determine how regional characteristics affect disaster aspects in terms of multiplicity and degree of damage.

We found that all the seismic risk potentials from direct to indirect are, even under an equal seismic input, distinctive according to prefecture in reflecting the environmental background. Also, in prefectures having a giant urban area, there is a dominant tendency for the spread from immediate disasters towards subsequent disasters and socio-economic impacts. These time-delayed and far-reaching effects decrease with the decreasing sizes of urban areas; in a prefecture having no large city, most aspects of the disaster are confined to immediate ones, no significant sequential character being observed. Therefore, regional disaster mitigation programs should be prepared optimally in consideration of such sequential aspects caused by an earthquake.

Key words

regional seismic risk, systems approach, disaster chain